You can fix font rendering by using the JDK provided with intellij-idea-ce [1]. To do this, set CLION_JDK=/opt/intellij-idea-ce/jbr/ or write /opt/intellij-idea-ce/jbr/ to ~/.CLion2019.3/config/clion.jdk

@Zrax: could you add some additional files to the backup array in PKGBUILD? Specifically:
- opt/${pkgbase}/bin/clion.vmoptions
- opt/${pkgbase}/bin/idea.properties
These contain settings for the user to change.